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SubjectRe: [REGRESSION] 41c7f74 rtc: Disable the alarm in the hardware (v2)
---- On Thu, 12 Dec 2013 22:16:55 +0100 John Stultz<john.stultz@linaro.org> wrote ---- 

> On 12/12/2013 11:39 AM, John Stultz wrote:
> > On 12/05/2013 03:51 AM, Brecht Machiels wrote:
> >> On Mon, 02 Dec 2013 22:19:58 +0100, Borislav Petkov wrote:
> >>
> >>> On Mon, Dec 02, 2013 at 12:47:17PM -0800, John Stultz wrote:
> >>>> Ok, sorry about this. I've been hoping we'd get some better insight
> >>>> into what's actually happening on these strange BIOSes where disabling
> >>>> the irq seems to cause it to scream (powering the system back on when
> >>>> its shutdown), in the hopes of having a proper workaround. But despite
> >>>> Borislav's efforts, he didn't seem to be able to root cause the issue.
> >>> Right, this bug is too nasty - you could generate good random numbers
> >>> just from how the hardware behaves. :) And I've been trying to make
> >>> sense of what happens but I failed, as you know. :(
> >>>
> >>> I consider it a huge waste of time and efforts having to deal with such
> >>> b0rked hardware instead of throwing it out of the window into the poring
> >>> rain while it is still powered.
> >>>
> >>>> Borislav, could you double check this patch still works on your
> >>>> hardware as well?
> >>> Well, we have the patch in SLES11:
> >>>
> >>> http://kernel.opensuse.org/cgit/kernel/commit/?h=SLE11-
> >> SP3&id=835398eb94dca7d55acd1a2628372e602ae3252a
> >>> and it passed testing.
> >>>
> >>> From what I see below, your version is equivalent to the one above with
> >>> the logic reversed so it should work. I'll still try to get that
> >>> affected box and run your version on it but it'll take a while.
> >> Hello John and Boris,
> >>
> >> Thank you for your quick response. And no need for an apology, I can
> >> understand your frustration with the way some hardware behaves.
> >>
> >> I ran with John's patch for a couple of days, and it seems to work.
> >> Curiously, the laptop did spontaneously boot the first time that I shut
> >> it down with the patched kernel. I have no conclusive explanation for
> >> this, but I have noticed that a manual power down is necessary after
> >> booting with an unpatched kernel. Simply rebooting with a patched kernel
> >> is not enough to stop the spontaneous boots. As far as I can remember, I
> >> went directly from my custom kernel (with the v2 patch reverted) to a
> >> kernel with your patch applied, so I'm not 100% convinced everything is
> >> all right. I should say that I did experience some spontaneous boots when
> >> running only Windows XP in the past, so there may be occasions where
> >> drivers might not be able to help at all.
> > Yea. It seems almost like the RTC_AIE bit is inverted in the hardware or
> > something.
> >
> >> Thankfully, after other shutdowns/hibernates (about 6 in total) the
> >> laptop never booted spontaneously.
> >>
> >> As for killing alarm functionality on the affected systems, I did some
> >> quick tests. With the patched kernel, I can set the RTC alarm by echoing
> >> to /sys/class/rtc/rtc0/wakealarm, and the machine will boot at the
> >> specified time. I have also tried setting the RTC alarm, and then
> >> disabling it again by echoing '0' to /sys/class/rtc/rtc0/wakealarm. While
> >> this sets the alrm_time to five minutes in the future, alarm_IRQ is set
> >> to 'no' and the machine does *not* boot spontaneously 5 minutes after
> >> shutting down. So, all seems well, as far as I can see. Unfortunately, I
> >> don't know enough about the RTC driver to draw any conclusions from this.
> > Ok. Sounds like the patch works fairly well then. I'll go ahead and
> > queue it for 3.14 and -stable.
> Brecht: Is it OK if I add to the patch:
> Tested-by: Brecht Machiels <brecht@mos6581.org>

Sure.

Thanks,
Brecht



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